Improvement in collapsible scfiew-taps



J. M. JOHNSON Collapsible Screw-Tap.

No.198,945. Patented Jan. 8,1878.

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JAMES M. JOHNSON, OF CLEVELAND, OHIO, ASSIGNOR OF ONE-HALF HIS RIGHT TOANDREW PARKER, OF SAME PLACE.

IMPROVEMENT IN COLLAPSIBLE SCREW-TAPS.

Specification forming part of Letters Patent No. 198,945, datedrJannary8, 1878; application filed September 21, 1877.

State of Ohio, have invented a new and use ful Collapsible Screw-Tap,which is fully set forth in the following specification and accompanyingdrawings, in which- Figure 1 is a longitudinal section, Fig. 2, a

side elevation Fig. 3, a side elevation,reverse' of Fig. 2 and Fig. 4,an end view.

The object of my invention is to furnish a device bywhich to collapsethe cutting-dies in a screw-thread cutting-tap, so that when thescrew-thread has been cut the dies may be closed up to enable the tap tobe withdrawn without the necessity of a reverse rotary motion.

In the drawing, A is a hollow mandrel, provided at the cutting end withslots or seats for the cutting-dies B B. C is a sliding rod, fittedwithin the said mandrel A. Its forward end is enlarged, and is providedwith slots whose bottom surfaces are made at an inclination from thecenter line. Surrounding the enlarged portion of the mandrel A is asleeve,

D, in which is made one straight circumfen. ential slot, d, and onediagonal circumferential slot, (1 Through the slot d is placed a pin, 0which is fixed in the mandrel A, and through the slot (1 is placed apin, 0, which also passes through a longitudinal slot, (1 in themandrel, and'is fixed in the rod C.

B B are the cutting-dies, lower edge of which is made inclinedcorrespondingly with the bottoms of their seats in the end of the rod C.The said dies also have a slot cut in one side near their lower inclinededge, in which a feather at one side of the slots in the said rod 0fits, and is for the purposeof preventing the dies from slipping out.

.In the sides of the mandrel, at the forward end, are placedreaming-dies g 9. To the side of the sleeve D is placed an adjustablestop, h, to adjust the throw of the sleeve. To move the-sleeve, a shortlever, l, is used.

It will be seen from theforegoing that when the rod C is in the positionseen in the drawing the dies B are pushed out, that their cutting-edgesproject beyond the circumference of the mandrel, in which position theyare designed to do their work. When they have done their cutting, byturning the sleeve D the diagonal slot d carries the pin 6 and draws therod 0 backward, by which means the dies B B are closed together. Thenthe tap can be withdrawn without making revolutions, thus saving timeand wear of machinery.

These taps can be made in a variety of sizes, from half-inch to eightinches, and are found to be exceedingly convenient for tapping gas andwater pipes and their connections.

It will also be observed that the stop h also J.

serves as a gage for the depth of out, which can be adjusted more orless, as may be required.

Having described my invention, I claim The hollow mandrel A, having thelongif

